Cooling of dynamo-electric machines



Jan. 6, 1925. 1,522,333

G. SCHROEDER COOLING OF DYNAMO ELECTRIC MACHINES Filed Oct.- 30, 1920 2Sheets-Sheet 1 2 Sheets-Sheet 2 G. SCHROEDER Filed Oct. 30. 1920 COOLINGOF DYNAMO ELECTRIC MACHINES lJan. 6, 1925.

Patented Jan. 6, 1925e PATENT OFFICE.

GIULIO SCERCEDER, OI ENGLAND.

COOLING OF DYNAwO-ELECTRIG MACHINES.

Application tiled, october S30, i920.

To all whom t may] concern:

Be it known that I, GIULIO Sormornnr., a subject of the King of Italy,residing in Hale, Cheshire, England, have invented certain new anduseful Improvements in the Cooling of Dynamo-Electric Machines, of whichthe following is a specilication.

This invention relates to the cooling arrangements of turbo 'alternatorsand other high speed electric machinery.

In machines of the kind to which this invention relates the limitationsto the possibility of the cooling of the rotor greatly influence theoutput that can be obtained from a given size of machine. rl`his is dueto the greater difliculty of supplying cooling fluid in suflicientquantities to the rotor than to the stator, and to the difficulty inapplying the cooling fluid near those parts of the rotor where the heatis generated7 principally owing to the mechanical requirem ents of thestructure.

In accordance with this invention the cooling arrangements are dividedinto two concentric systems and the gaseous cooling fluids supplied tothe two systems are different in that the fluid for the inner system hasa materially greater heat absorbing capacity per unit volume within thetemperature limits permissible in the machine than the fluid supplied tothe outer system. In general air will be the fluid employed and the heatabsorbing capacity of the supply to the inner system will be increasedby passing that air through a refrigerating plant so that itstemperature at admission to the machine is reduced below the temperatureof the surrounding atmosphere, After leaving the inner system the air orother gaseous fluid may be either discharged outside or circulated orpassed into tie outer cooling system.

rI`he inner system will deal with the interior of the rotor and theintensified cooling which it provides will give the result that therotor temperature need no longer be a limitation to the output of largehigh speed machines.

The invention will be further described by the aid of the accompanyingdrawings in which Figure l shows in vertical section a Serial No.420,667.

machine to which the invention is applied; Figure 2 shows a transversesection through the rotor shown in Figure l; Figure 3 shows an insideelevation of the member in which the air inlet and outlet passages forthe machine are formed; Figure 4l shows a section on the line IV-IV ofFigure 3; Figure 5 shows in vertical section a machine similar to thatshown in Figure 1 but embodying a modification at the outlet end of therotor; Figure 6 shows in elevation an arrangement of apparatus forproducing the cooling and compressing of the cooling fluid for the r0-tor.

In the form shown in Figures l-4 the cooling gaseous fluid for the rotorflows in a closed circuit through the rotor and through a refrigeratoras indicated by the arrows so as to avoid the continual drawing in oflarge quantities of fresh fluid which may bring with them a considerableamount of dust which may accumulate in the rotor passages. In thiscirculation the air passes through a refrigerating chamber A in which itflows over cooling coils which may be arranged in two sets, to the firstof which water at approximately atmospheric temperature from anyconvenient cold supply is delivered while in the second brine or othersuitable liquid from a refrigerator flows. rEhe connections for thewater supply are indicated at B and those for the` refrigerating liquidare shown at C. A centrifugal blower or compressor D takes the air as itcomes from the chamber A and drives itforward through the duct E to theinlet end of the rotor, making connection with the admission chamber F.This chamber leads the air to the inlet end of axial passages throughthe rotor and from the other end of these passages the air passes intothe outlet chamber G similar in form to the chamber F. To this chamberis attached a duct I-I which completes the circuit back to the chamberA.

In arranging the circulation of the fluid through the rotor the axialpassages will preferably be so located as to produce an approximation touniformity of temperature of the teeth and of the metal adjacent to theroots of the teeth. In the arrangey ment illustrated the axial passagesare shown at .l as formed by continuations ot the slots so that the airflows directly in contact with the coils and with the metal at the rootsoi the teeth.

As shown in Figures le and ti, the member in which the admission chamberF tor the rotor air is formed also provides in the usual way a passagefor conducting air to the stator cooling system. This passage is lreptquite distinct from the chamber F but surrounds it on both sides so thatthe two streams oil cooling tluid tor rotor and stator respectively passupward into the machine side by side but are kept apart. In thearrangement shown in Figure l the construction of this member is thesame at each end of the machine, the only difference being that at theoutlet end the rotor air is owing down and the stator air is flowingupward, the stator cooling system being ot a. type in which the airenters at both ends and flows axially and then radially, leaving by anout let at the top ot' the machine as indicated by the arrows.

It is to be noted that where the air passes from a stationary to arotating part. and vice versa, a lioint is made having small clearanceor rubbing contact so as to minimize leakage from the rotorcoolingsystemeither to the stator cooling' srstcru or lo the externalair. 'llo take care oit small un avoidable leakage an inlet in: beprovided on the suction side of the s v n rontroliefl by a non-returnvalve .l wliieh iieriuitfa ihh iniow of makeup air when the pressurefalls below a determined value.

In many cases it will be preterable to pro fide that the coolingy tluidbe sont through the rotor under a pressure considerably aboveatmospheric so as to obtain an increased heat transn'iitting capacit)vfor a given area ot rotor duet surface.

Figure 5 illustrates an alternative ar rangement; in which a closedcirculation system tor the rotor air not used. ln it the air coming fromthe outlet end o t the rotor 'Hows indicated by the arrows to join theincoming' air at that end ot the stator and passes with it into thestator cooling system leaving` that system by the outlet shown at thetop ot the ligure. lith suoli a construction it is unnecessary toprovide an outlet chamber such an indicated at Gr in Figure l, andaccordiuglyY the stator air inlet is ot an ordinary construction at thisend, that is to say, it has the torni shown in Figures Il and 13, excepttor the omission ot the wall separating the part F trom the rest o't thespace enclosed by the cover. As the duet Hot Figure Yl is on'iitted inFigure it will he obviousl that the refrigerator inlet (H oit' Figuretil will i ceive air from the atmosphere.

By the terni refrigeration used herein,

it is intended to indicate the lowering of the temperature of thegaseous Huid to a point materially below the temperature ot' thesurrounding atniospherc.

lt will be understood that the illustrations given are only by way otexample and. that the relative arrangement and proportions of the plantshown in the figures are only diagrammatic.

that I claim as my invention and desire to secure by Letters Patent is:

l. The combination ot a dynamo electric machine having Ventilatingpassages ar ranged in the machine structure to torm two concentricsystems, the outer system serving lor the exterior ot' the rotor and forthe stator and the inner system tor the interior ol" the rotor andcon'iprising ducts in the rotor body and an inlet chamber toi-ming partot the stationary structure of the machine adjiacent one end ottherotor, the, said chamber enclosingl the inlet ends ot' the ducts andseparating them trom the outer system, and means for supplying the twosystems with gaseous fluid at ditlerent telnperatures, the colder fluidbeing ted to the inner system.

2. The combination of a dynamo electric machine having Ventilatingpassages arranged in its structure to 'form inner and outer concentricsystems. the inner system serving tor the interior ot the rotor and theouter system 'tor the exterior ot the rotor and tor the stator and eachsystem comprisv ing an inlet chamber formed in one and the same.stationary end part ot the inachine structure, the inlet chamber forthe inner system lying` inside that tor the outer :"ivstem` and meanstor supplying the two systems with gaseous fiuids (littering inteuiperature, the colder tluid being ted into the inner inlet chamber.

3. The combination of a dynamo-electric machine having ii'entilatingpassages arU ranged in the machine structure to torni two concentricsystems. the outer system serving for the exterior ot thc rotor and torthe stator and the inner system for the interior of the rotor andcomprising ducts in the rotor body and an inlet chamber Atorming 5 partot the stationary structure ot the luachine adjacent one end of therotor. the said chamber enclosing the inlet ends ot'A the ducts andseparating them trom the outer system. means tor supplying the twosystems 130 with separate bodies ot gaseous tluid` and means torrirfrigerating one ot such bodies so that the fluid 'ted to the innersvsten'l is colder than that iled to the outer s stem or than theadjacent atmosphere.

4. The conibination ot a (.l \uiamo-elertrie machine having ventilatingpassages :ir ranged in its structure to form inner and outer concentricsystems, the outer system having an inlet chamber at each end of the umachine, and the inner system having an inlet Chamber at one end of themachine, nieans 'for leading the discharge from the inner system into aninlet chamber for the outer system, means for supplying to the twosystems 'from two external sources separate bodies of gaseous coolinguid, and

means for refrigeratng one of said bodies so that the fluid fed to theinner system is colder than that fed to the outer system or 10 than theadjacent atmosphere.

In testimonyv whereof I afix iny signature.

GIULIO SCHROEDER.

